Just acquired a CZJ Biotar 2/58. From images of the lens, I fully expected it to be large and heavy, like the Rokkor. Instead, it is tiny and as light as a feather. It is similar in weight to the plastic Sigma 35mm for NEX.

Hello all, I just registered to this forum, but have been following this thread for a while. I use four Zeiss ZK lenses on a Pentax K5IIs, and have consequently sold all my other lenses. You could say I love the look and the handling of these modern Zeiss primes. My last buy was the distagon 28/2, and recently I got to use it a lot on a trip abroad. In preparing some 24 inch prints, I noticed for the first time that the right side of the image shows less detail than the left side. Shooting at 5,6/6,3 at infinity, the detail just isn't there any more on the far right side.
Now, of course this is at 100% viewing, and it is not something I can not live with, having the option to further stop down, but the lens just isn't up there with the other Zeiss lenses, e.g. my distagon 35/2. Moreover, I plan to upgrade to FF when Pentax releases it, and it should be more severe on FF.
I sent an email to Zeiss, and they very kindly attached a repair form in the reply, suggesting I send it in. Still, I am uncertain if I should have it serviced, as decentering (which I assume this is), is generally not serviceable, am I right?
Zeiss no longer makes the ZK lenses, so I can not have it replaced.
Has anyone experience with a similar situation?
I dread the idea of the lens away, and taken apart, and having it returned only to see no improvement.
Anny suggestions?
I will post some examples/ crops this evening.
Thanks in advance
Chris

Decentering is of course in general possible to fix. You simply replace the parts which aren't right, such as the glass, the housing, etc. I think what you might be referring to is that manufacturers sometimes get a lens in, "fix" something, and it returns still not right. I don't recall having heard Zeiss doing something like that. I would try it out.

I had once a decentered Planar 1.4/85 and sent it to Zeiss. I bought it used and had no invoice to claim warranty service.
After some emails with explenations and test shots, they fixed most of the decentering and set a precise infinity stop to compensate slight field curvature. I got even test shots from the engineer before and after the adjustments.